If it's 'constructive' and 'criticism', it's an Oxymoron. However, 'constructive' truly a tag picked up voluntarily and the procedure is purely subjective. If ever someone feels hurt, he should leave the field to the others. There is a concept called 'Swakucha mardanam' that implies self-gratification (because none else is coming forward to do it, without hurting). A discussion or even a forum for it permits no self-centered human emotions.